Focal mechanism of shear-tensile microseismic and amplitude distribution characteristics
Tang Jie1,2, Wang Hao1,2, Wen Lei1,2, Zhang Wenzheng1,2
1. School of Geosciences, China University of Petroleum(East China), Qingdao, Shandong 266580, China; 2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China
Abstract:Microseismic events induced by hydraulic fracturing contain many non-double couple types,shear tensile rupture may occur in rocks.Shear-tensile type microseismic show many differences in source and amplitude characteristics compared with shear type earthquake.We study in this paper the shear-tensile mechanism,and analyze shear-tensile source microseismic radiation pattern and energy propagation characteristics.The main understandings are included:A.Shear-tensile sources generate shear and tensile motions and the source tensor can be described with strike,dip,rake,and tensile angle;B.Moment tensors of shear-tensile source can be decomposed to double-couple (DC) and non-double-couple (Non-DC) components.Non-double-couple components comprise the compensated linear vector dipole (CLVD) and the isotropic (ISO) component;C.Radiation energy of shear-tensile source will change with the tensile angle,the amplitude distribution at surface receivers is relative to focal mechanism,model parameters,and sensor positions.Based on study of the focal mechanism and amplitude distribution characteristics of shear-tensile microseismic,we can get a better understanding of the source characteristics and signal distribution.
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